Aerator devices, in particular strip-like aerator devices, also called strip diffusers, are known in various embodiments in the art, cf. for instance WO 2009/132374 A2, U.S. Pat. No. 7,255,333 B2, U.S. Pat. No. 6,406,005 B1, and U.S. Pat. No. 6,344,147 B1. Such aerator devices are used in aerating waste water in activated sludge plants. During use, gas, in particular air, is supplied to the space between the base member and the perforated membrane attached to the base member; in most embodiments, the perforated elastic membrane is bulged upwardly, and gas or air passes through the perforations in the membrane upwardly into the waste water in form of gas bubbles. As already mentioned, these structures and functions are well known in the art so that no further description is needed here.
Usually, the perforated elastic membrane is made of polyurethane (PU) which may be adversely affected by UV radiation. When aerator devices or strip diffusers as mentioned above are produced and delivered, they are often stored in free areas so that the PU membrane is exposed to sunshine comprising the adverse UV radiation. Therefore, the perforated PU membranes may be deteriorated so that, when finally installed, the function of the perforated PU membrane is reduced and the term of operation is shortened.